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Photosynthesis
Concept 8: Cooperation of the Light Reactions and the Calvin Cycle
Photosynthesis depends on an interaction between two sets of reactions: the light reactions and the Calvin cycle. Chlorophyll and the other molecules responsible for the light reactions are built into the thylakoid membranes. The enzymes that catalyze the Calvin cycle are located in the stroma. Beginning with the absorption of light by chlorophyll, the light reactions convert light energy into chemical energy in the form of ATP and NADPH. The ATP provides the energy, and the NADPH supplies the electrons for the Calvin cycle, which converts carbon dioxide to sugar. The ADP and NADP+ that result from the Calvin cycle shuttle back to the light reactions, which regenerate ATP and NADPH.